Patent GB-996975-A (GB)
Title: Semi-conductive films and methods of producing them
Inventor: HUGLE FRANCES BETTY
IPC: C23C14/58
Filed: 1961-07-31
Abstract: A semi-conductive film of a compound is made from anionic and cationic elements (defined in the Specification) by selecting one of cadmium, lead, indium, mercury, gallium, zinc, aluminium, arsenic and antimony as the cationic element, and one of sulphur, selenium, tellurium, antimony and arsenic as the anionic element, the two elements having disparate vaporization temperatures and forming a a compound having a higher vaporization temperature than that of one of the elements, vaporizing the elements separately and successively in a vacuum so as to deposit the elements as discrete films superposed upon each other on a substrate, in which films the element of lower vaporization temperature is in excess, and thereafter heat treating the films to produce a reaction between the elements, at least a portion of this treatment being at a temperature above the vaporization temperature of the element of lower vaporization temperature.  As an impurity, one of cerium, chromium, tin, manganese, silver and copper, or tellurium, arsenic, or antimony when none of these three elements is used as the anionic or cationic elements, may be added to at least one of the elements prior to vaporization.  The superposed films may comprise two films of the anionic element enclosing a film of the cationic element, and the heat treatment may be in air, in an inert atmosphere or in vacuum. The substrate may carry on its surface spaced elements of a printed circuit, certain areas of the substrate may be masked with a masking substance prior to the formation of the superposed films thus restricting the formation to an area in electrical contact with the spaced elements, the masking material being removed prior to the heat treatment, and the semi-conductive film may be deposited in a position to contact the spaced elements of the printed circuit at least in part.  In Example 1, a photosensitive lead selenide film is formed on a glass slide substrate.  The cationic and anionic elements may be cadmium and selenium respectively, in which case the heat treatment may be at a temperature of from 300 DEG  C. to 400 DEG  C. in air for a time of one hour; this is exemplified in Example 2 in which a cadmium selenide film is formed by successive depositions of selenium, cadmium, and further selenium on a glass substrate on which a printed circuit had previously been formed, such a structure being suitable for use as a photo-electric cell. The cadmium selenide photo-cell of Example 3, otherwise made as for Example 2, has silver added to the cadmium as an impurity prior to vaporization.ALSO:A semi-conductive film of a compound is made from anionic and cationic elements (defined in the Specification) by selecting one of cadmium, lead, indium, mercury, gallium, zinc, aluminium, arsenic and antimony as the cationic element, and one of sulphur, selenium, tellurium, antimony and arsenic as the anionic element, the two elements having disparate vaporization temperatures and forming a compound having a higher vaporization temperature than that of one of the elements, vaporizing the elements separately and successively in a vacuum so as to deposit the elements as discrete films superposed upon each other on a substrate, in which films the element of lower vaporization temperature is in excess, and thereafter heat treating the films to produce a reaction between the elements, at least a portion of this treatment being at a temperature above the vaporization temperature of the element of lower vaporization temperature. As an impurity, one of cerium, chromium, tin, manganese, silver and copper, or tellurium, arsenic, or antimony when none of these three elements is used as the anionic or cationic elements, may be added to at least one of the elements prior to vaporization.  The superposed films may comprise two films of the anionic element enclosing a film of the cationic element, and the heat treatment may be in air, in an inert atmosphere or in vacuum.  The substrate, which may be, for example, glasses or ceramics, may carry on its surface spaced elements of a printed circuit, certain areas of the substrate may be masked with a masking substance prior to the formation of the superposed films thus restricting the formation to an area in electrical contact with the spaced elements, the masking material being removed prior to the heat treatment, and the semi-conductive film may be deposited in a position to contact the spaced elements of the printed circuit at least in part.  In Example 1, a lead selenide film is formed on a glass slide substrate. The cationic and anionic elements may be cadmuim and selenium respectively, in which case the heat treatment may be at a temperature of from 300-400  DEG C. in air for a time of one hour; this is exemplified in Example 2 in which a cadmium selenide film is formed by successive depositions of selenium, cadmium and further selenium on a glass substrate on which a printed circuit had previously been formed. In Example 3, otherwise similar to Example 2, silver is added to the cadmium as an impurity prior to vaporization.